'use strict';

// Do this as the first thing so that any code reading it knows the right env.
process.env.BABEL_ENV = 'production';
process.env.NODE_ENV = 'production';

// Makes the script crash on unhandled rejections instead of silently
// ignoring them. In the future, promise rejections that are not handled will
// terminate the Node.js process with a non-zero exit code.
process.on('unhandledRejection', err => {
  throw err;
});

const path = require('path');
const chalk = require('chalk');
const fs = require('fs-extra');
const webpack = require('webpack');
const checkRequiredFiles = require('react-dev-utils/checkRequiredFiles');
const formatWebpackMessages = require('react-dev-utils/formatWebpackMessages');
const printHostingInstructions = require('react-dev-utils/printHostingInstructions');
const FileSizeReporter = require('react-dev-utils/FileSizeReporter');
const printBuildError = require('react-dev-utils/printBuildError');
const config = require('../config/index')
const webpackConfig = require('../config/webpack.config.pack');

// These sizes are pretty large. We'll warn for bundles exceeding them.
const WARN_AFTER_BUNDLE_GZIP_SIZE = 512 * 1024;
const WARN_AFTER_CHUNK_GZIP_SIZE = 1024 * 1024;

// 如果缺少必需的文件，则发出警告并崩溃
if (!checkRequiredFiles([config.pack.entry])) {
  process.exit(1);
}

// 创建生产版本并打印部署说明。
function build(previousFileSizes) {
  console.log('Creating an optimized production build...');
  let compiler = webpack(webpackConfig);
  return new Promise((resolve, reject) => {
    compiler.run((err, stats) => {
      if (err) {
        return reject(err);
      }
      const messages = formatWebpackMessages(stats.toJson({}, true));
      if (messages.errors.length) {
        // Only keep the first error. Others are often indicative
        // of the same problem, but confuse the reader with noise.
        if (messages.errors.length > 1) {
          messages.errors.length = 1;
        }
        return reject(new Error(messages.errors.join('\n\n')));
      }
      if (
        process.env.CI &&
        (typeof process.env.CI !== 'string' ||
          process.env.CI.toLowerCase() !== 'false') &&
        messages.warnings.length
      ) {
        console.log(
          chalk.yellow(
            '\nTreating warnings as errors because process.env.CI = true.\n' +
              'Most CI servers set it automatically.\n'
          )
        );
        return reject(new Error(messages.warnings.join('\n\n')));
      }
      return resolve({
        stats,
        previousFileSizes,
        warnings: messages.warnings,
      });
    });
  });
}

//首先，在生成目录中读取当前文件大小。
//这可以让我们显示它们后来改变了多少。
FileSizeReporter.measureFileSizesBeforeBuild(config.pack.outputPath)
  .then(previousFileSizes => {
    // 清空文件加
    fs.emptyDirSync(config.pack.outputPath);
    // 开始webpack打包
    return build(previousFileSizes);
  })
  .then(
    ({ stats, previousFileSizes, warnings }) => {
      if (warnings.length) {
        console.log(chalk.yellow('Compiled with warnings.\n'));
        console.log(warnings.join('\n\n'));
        console.log(
          '\nSearch for the ' +
            chalk.underline(chalk.yellow('keywords')) +
            ' to learn more about each warning.'
        );
        console.log(
          'To ignore, add ' +
            chalk.cyan('// eslint-disable-next-line') +
            ' to the line before.\n'
        );
      } else {
        console.log(chalk.green('Compiled successfully.\n'));
      }

      console.log('File sizes after gzip:\n');
      FileSizeReporter.printFileSizesAfterBuild(
        stats,
        previousFileSizes,
        config.pack.outputPath,
        WARN_AFTER_BUNDLE_GZIP_SIZE,
        WARN_AFTER_CHUNK_GZIP_SIZE
      );
      console.log();

      // const appPackage = require(paths.appPackageJson);
      // const publicUrl = paths.publicUrl;
      // const publicPath = config.output.publicPath;
      // const buildFolder = path.relative(process.cwd(), paths.dist);
      // printHostingInstructions(
      //   appPackage,
      //   publicUrl,
      //   publicPath,
      //   buildFolder,
      //   useYarn
      // );
    },
    err => {
      console.log(chalk.red('Failed to compile.\n'));
      printBuildError(err);
      process.exit(1);
    }
  );
